If smaller snails are available they usually won't attack larger snails like nerites and mysteries. But if hungry they might try and also assassins can gang up to kill a snail that might seem too big for one assassin to kill.I have a few questions about snails.
1. I read some where that assassin snails will not kill nerite snails is that true?
2. Will nerite snails breed in freshwater?
3. How many nerite snails would you recomend as a algee crew for a 55G?
None of the ones available for sale in the US will but there actually are some true freshwater nerite species in Europe.
Nerites lay eggs in freshwater even if they don't hatch. Since their are around 4-6 species of nerites offered for sale to the freshwater market you might as well get one of each then they won't breed and lay eggs. That's what I would do if I had a 55g, but one nerite is enough for my 10g.